The present invention relates to a food composition for domestic carnivores which makes it possible to prevent or correct pigmentation abnormalities and/or to improve the quality of the fur of the said domestic carnivores, characterized in that it contains a source of free tyrosine representing at least 5% of the total tyrosine supplied. The invention also relates to a veterinary composition containing tyrosine, as well as the use of free tyrosine for the preparation of a food and/or veterinary composition intended for preventing pigmentation abnormalities and/or for improving the quality of the fur in a domestic carnivore.
Despite a rich and nutritionally well-balanced diet, in particular as regards the supply of proteins and amino acids, many breeders or owners of domestic carnivores, particularly dogs and cats, complain of abnormalities in the pigmentation of their animals.
These xe2x80x9cdiscolorationsxe2x80x9d cause them substantial financial losses, particularly during competitions, the animals displaying these abnormalities being systematically downgraded or even eliminated by xe2x80x9cjudgesxe2x80x9d who know the xe2x80x9cstandardsxe2x80x9d of each breed of animal well.
Domestic carnivores designate dogs and cats, but also other animal species, and particularly animals having a coat, mink, fox, sable and the like.
These poor pigmentations may occur in the skin, the mucous membranes, the eyes, and more frequently in the hair.
The normal colour of these organs is the visual result of the deposits of several sorts of pigments:
nonmelanic pigments: blood pigments (oxyhaemoglobin, reduced hemoglobin, haemosiderin), carotene and its derivatives;
melanic pigments or melanins (eumelanins, phaeomelanins, trichochromes) (E. Guaguxc3xa8re et al., Le Point Vxc3xa9txc3xa9rinaire, 1985, vol. 17, No. 93, 549-557).
Among these pigments, it is mainly the eumelanins which give the black colour or the dark shade of the pigmentation of the organs.
It is known that the melanins are synthesized by organelles called melanosomes of the specialized cells called melanocytes, from tyrosine, a xe2x80x9csemi-essentialxe2x80x9d aromatic amino acid supplied by the dietary proteins. An amino acid is said to be xe2x80x9cessentialxe2x80x9d when it is necessarily supplied by a source which is external to the animal, because the latter itself does not know how to produce it. Thus, tyrosine is xe2x80x9csemi-essentialxe2x80x9d because the animal can synthesize it from another xe2x80x9cessentialxe2x80x9d aromatic amino acid, phenylalanine. Consequently, for example, the National Research Council (N.R.C.) of the United States of America, which is the world authority on animal nutrition, recommends the following nutritional standards for cats and dogs, based on the dry matter content of the foods, and of which only phenylalanine is considered as being essential (Nutrient Requirements of Cats, 1986; Nutrient Requirements of Dogs, 1985):
These standards have nevertheless currently been widely overtaken by balanced industrial foods which are considerably richer in proteins and in amino acids, and have consequently already a high content of tyrosine.
Yet, in spite of the richness of the current foods supplied by all the major international brands, breeders frequently complain of the pigmentation abnormalities in their animals, and particularly in their fur. Breeders and vets speak in this case of xe2x80x9cdecolorizationxe2x80x9d, of xe2x80x9cdiscolorationxe2x80x9d, of xe2x80x9cdepigmentationxe2x80x9d, of xe2x80x9cdispigmentationxe2x80x9d, of xe2x80x9cred hairxe2x80x9d, of xe2x80x9cyellow hairxe2x80x9d, of xe2x80x9cfaded hairxe2x80x9d, and the like, to designate this syndrome.
The nutritional aetiology of this syndrome is commonly excluded by vets and nutritionists (L. Case et al., Canine and Feline Nutrition, 1995, Mosby Ed., Saint Louis, USA, p 316-319). Particularly, Paragon and Granjean (Rec. Vxc3xa9t. Mxc3xa9d., 1992168(10), 769-77) have excluded a possible deficiency of tyrosine in dogs and cats normally fed in practical conditions.
Only one team in the Ecole Nationale Vxc3xa9txc3xa9rinaire de Toulouse has described in dogs a xe2x80x9crubra-pilaris syndromexe2x80x9d or red hair disease which can have a nutritional cause (P. Dorchies et al., Revue de Mxc3xa9dxc3xa9cine Vxc3xa9txc3xa9rinaire, 1979, 130 (10), 13711382). Indeed, the syndrome is accompanied by an increase in the level of blood and urinary indican. This high presence of indican in the blood and the urine is a sign of a poor digestive use of an essential amino acid, tryptophan, because indican or potassium indoxylsulphate is a metabolite which is synthesized by the bacteria in the large intestine from dietary tryptophan.
The applicant has discovered that this phenomenon of pigmentation abnormality is due to a deficiency in free tyrosine in the diet.
The applicant has indeed discovered that in order to prevent pigmentation abnormalities and/or correct them when they exist in domestic carnivores fed with current balanced foods which have aromatic amino acids, in particular tyrosine, supplied well above the known recommended standards (such as those of N.R.C., for example), it is essential that part of the tyrosine is supplied to the animal in free form and that the tyrosine supply does not exist solely and completely in bound tyrosine form. This discovery is valid regardless of the level of aromatic amino acid contents in the foods, provided that they are equal to or above the recommended nutritional standards.
Conventionally, an amino acid is said to be xe2x80x9cboundxe2x80x9d when it is embedded in the structure of a protein. To be able to assay a bound amino acid, the protein should be previously and completely hydrolysed, most often with a protease or a strong acid or a strong base. This is the case for the amino acids supplied by the proteins in the dietary raw materials commonly used, whether they are of animal or plant or microbial or fungal origin.
An amino acid is said to be xe2x80x9cfreexe2x80x9d when its assay does not require prior hydrolysis with a protease or a strong acid or a strong base. To assay a free amino acid in a food, it must simply be separated from the structured proteins by precipitating them, with a protein coagulant such as trichloroacetic acid or sulphosalicylic acid for example. After separating the structured proteins, the free amino acid can then be assayed by any known means, such as liquid chromatography for example.
The applicant has discovered, surprisingly, that when at least 5% of the total supplied tyrosine, and still more preferably at least 10%, 15%, 20%, 25% or 30% is supplied to the animal in free form, it is possible to prevent the pigmentation abnormalities in domestic carnivores and/or to treat them when they exist. It is necessary for the free tyrosine to be supplied to the animal, regardless of the quantity of bound tyrosine supplied.
Thus, the invention relates to a domestic carnivore food composition for preventing pigmentation abnormalities and/or improving the quality of the fur, characterized in that it contains:
at least one source of proteins of animal or plant origin, and/or
at least one source of fatty substances of animal or plant origin, and/or
at least one source of rapid or slow carbohydrates, in particular cereals, and
one source of free tyrosine representing at least 5% of the total tyrosine supplied.
In another embodiment of the invention, the free tyrosine level in the food composition will be greater than 10% of the total tyrosine supplied.
In another embodiment, the food composition already contains a level of tyrosine that is well above the nutritional standards as mentioned above.
The invention also relates to a domestic carnivore veterinary composition for preventing pigmentation abnormalities and/or improving the quality of the fur, characterized in that it contains a source of free tyrosine representing at least 5%, and preferably at least 10%, 15%, 20%, 25% or 30% of the total tyrosine supplied in the diet.
The applicant has therefore developed a method for preventing pigmentation abnormalities and/or improving the quality of the fur in domestic carnivore, characterized in that a quantity of free tyrosine greater than 5%, or preferably 10%, 15%, 20%, 25% or 30% of the quantity of total tyrosine supplied in the diet of the said carnivore is administered to the said carnivore. This process, notably for its esthetic result, is also one of the subjects of the present invention.
The food compositions according to the invention may be dry foods such as biscuits for example, semi-moist foods, for example pates and the like, or moist foods. These foods also comprise snacks, treats or extruded foods, as well as nutritional supplements.
The veterinary compositions according to the invention include compositions which can be administered by the oral, parenteral or dermal route.
Preferably, the veterinary composition will be administered by the oral or parenteral route or by the gastrodigestive system. Thus, the veterinary composition according to the invention may be in particular, without this list being limiting, an intragastric, intraintestinal, intramuscular, subcutaneous or intravenous infuision, a hard gelatine capsule, a pill, a soft gelatine capsule, a bolus, a suppository or any other presentation which can be administered by the digestive route.
Conventional excipients may be added to this veterinary composition, such as gelatine, starch, lactose, magnesium stearate, talc, gum arabic and the like.
The free tyrosine supply may consist of L-tyrosine and/or its salts. Commercially available L-tyrosine may be obtained by extraction after enzymatic or chemical hydrolysis of various animal, plant, microbial or fungal proteins or by any other process known to amino acid producers. It is also possible to use as free tyrosine source a protein which is completely or partially hydrolysed (with a protease, an acid or a base), whether the original protein is of animal, plant, microbial or fungal origin, without the free tyrosine being separated from the rest of the amino acids.
The applicant has also discovered that, particularly in the fur of animals, the supply of free tyrosine improves not only the pigmentation but also the quality of the fur, mainly the density and the length of the hair.
The examples which follow are intended to illustrate some aspects of the invention without, however, being limiting.